The invention relates to a metering pump for pumping a metering agent to a metering point. The invention relates in particular to a metering pump with a pump chamber comprising a diaphragm and being adapted to be connected with a metering agent tank through a suction conduit having a suction valve, and an automatic bleed system and a return conduit comprising a first head valve.
A metering pump of this kind is known from the German patent application No. 26 51 614.3. The diaphragm pump operates as predelivery pump. In addition there is provided a piston pump with the required piston packings operating as metering pump. When used for metering aggressive media, the piston packings have a limited service life such that such pumps are not suitable for the metering of aggressive media.
Metering pumps for aggressive media are known. However, they have the problem that air or gas gathers in the pump chamber and the output of the pump decreases until the pump is ventilated or bleeded by hand. This is in particular a drawback when outgasing media are used and metering agent tanks are exchanged.